ios 11 camera has black screen

Either swiping on locked screen or opening the Camera App, it often opens the App with the screen black. However, you can take a photo and view it but the screen remains black. Force quit or reboot makes no difference. The only way so far has been to first open StageCam App and then iPhone Camera App also starts to work. Also when both Apps are on simultaneously.

iP8 Plus and latest Apps and iOS version, Mika